Method of producing printing forms from colloids



Patented July 27, 1943 METHOD or reonpcmc rmn'rnvc Forms FROM coLLoms aJosef Kc h,

Siegburg, Germany; vested inthe Alien Property Custodian t No Drawing.Application August z 2, 1939, Serial No. 291,379. In Germany'August 24,1938 Q 2 Claims. (ores- 5.4)

The present invention relates to a method of producing printing fromdiapositives and letterpress to be printed a screened copy in knownmanner is first prepared on a colloid film, which is then transferred toaprinting form carrier, and is developed and dried after rier.

According to the invention the colloid film is applied to a smooth filmcarrier and copied through to the positions on the screen and in whiteas far as the base. The film carrier has to be separated from thecolloid film by means of a liquid, which dissolves the film carrierwithout any part of the colloid film being also dissolved. In this way aprinting form is obtained whose screen cross-lines lie in one plane withthe white and are of a uniform height so that the doctor blade can wipeoff the ink uniformly. The gelatine film may merely show in the screennaps themselves, differences in high lights and low lights and thegelatine film then forms a relief corresponding to the matter to beprinted.

The possibility of carrying out the method according to the invention isthus restricted to the possibility of copying-through as far as the filmcarrier the screen cross-lines uniformly in black and in white, so thatafter removing the film carrier by means of a liquid that does notattack the colloid film the screen cross-lines all lie in one plane.Celluloid foil, or foil of similar material, is suitable as film carrierof this kind. The actual film carrier may be applied subsequently upon alayer of paper. The dissolving of the film carrier from the colloid filmmay be effected by means of an etheric liquid as for example ethyl etheror acetone, or like liquids, which have a good capacity for dissolvingthe film carrier without on the other hand parts of the colloid filmbeing also dissolved.

It has already been proposed to make use of intaglio printing forms ofgelatine or asphalt without however the particular working conditionswhich form the condition for the realization of this proposal beingmentioned and recognized. When ordinary carbon paper is used, it iscertainly not possible to obtain printing surfaces of colloid films withuniformly high screen cross-lines, since when copying-through, theilluminated parts of the gelatine adhere so that the separation of thepaper without damage to the colloid film is quite impossible. It hasfurthermore been proposed to apply to the surface of the roller forphoto-chemical etching,

the removal of the film caritself the upper edges of forms from colloidsin which,

an uncopied film that is light-sensitive or that is to be madelight-sensitive later (the film be ing applied to a base film for thepurpose of obtaining a smooth surface) in such manner that the base filmthen forms an outer protectlve film which is to be dissolved by asolvent and which does notattack the colloid film itself. Apart from thefact that this method is described only in conjunction withphoto-chemical etching, itwould prove to be entirely unsuitable forproducing an intaglio printing form from the colloid film since, whenthe film is being copied after it has been applied to the surface of theroller, development is no longer pos- 'sible because when copying fromthe surface the insoluble relief is at the top while the unilluminatedparts and therefore the soluble parts a lie On the surface of theroller, so that when hot water is applied, dissolving of the base filmfrom the roller would be unavoidable. A sharp relief in the screen napswith uniformly high screen cross-lines cannot therefore be secured inaccordance with the matterto be printed.

The invention is hereinafter more fully described by reference to anexample:

For intaglio printing the printing form is produced in the followingmanner: As in the case of copper intaglio printing, a diapositive isprepared from the original to be printed, the diapositive being copiedupon alight sensitive colloid film. For copying purposes a film is usedmm; thick, the film being applied to a smooth film carrier-in thepresent case to Celluloid foil. The copying period must be so determinedthat copying-through is effected in the white and on the screencross-lines as far as the film carrier. After being damped the copy isapplied with its film side on the printing form carrier, in the presentcase upon a printing roller. The film carrier now covering the colloidfilm is dissolved by treatment with an acetone solution and therebyremoved. All the colloid film left on the roller is thn treated with hotwater of a temperature between and 60 0., whereby the unilluminatedparts of the colloid film. are washed away, the copied matter and thescreen cross-lines remaining in relief. After being dried the form isready for printing. For special cases the colloid film may be subjectedto subsequent dressing for exthe printing form consisting of the colloidfilm has been removed by simple washing.

In the same way are produced the printing forms for printing in relief,except that no screen naps are formed but more or less large raised anddried, the printing form in relief is ready for printing.

The method that process of the invention is employed, whole workingstages, such as etching, grinding of the copper, and the application ofThe elimination of the case I ings are commonly produced. completeelimination of the etching, 7 dependent upon correct observation andunderinvention is, unlike the known method,- com the production of newcopper layers,"

the printing form is made possible without previous knowledge. the

means the difficulties are avoided which are involved in three-colourprinting.

I claim:

1. The process of producing a printing form comprising preparing ascreened layer of photosensitive co-lloid which on exposure to lightbecomes water insoluble upon a sheet of soluble material, printing onthe uncovered side and fixing to and printed, applying the free thatonly, and washing unexposed portions of said colloid from said carrier.

2..The process of producing an intaglio printing form comprising forminga laminated sheet of Celluloid coated with a screened lightsensitivecolloid, fixing an image of the matter to be

